CNOOC Makes Ultra-Deep Gas Discovery in China's Bohai Sea

(Credit: CNOOC)

China's CNOOC has discovered a high-yield oil and gas well in ultra-deep volcanic formations in the Bohai Sea, with testing showing natural gas flow of approximately 800,000 cubic meters (28 million cubic feet) per day.

The well, located in central Bohai near the Bozhong Sag, encountered more than 120 metres of cumulative gas pay in volcanic formations and was completed at a depth of 5,770 metres, according to CNOOC.

The discovery marks a significant breakthrough in offshore ultra-deep natural gas exploration, opening a new geological play in an area where complex subsurface conditions have made reservoir prediction difficult, according to the company.

CNOOC said it used independently developed multi-source broadband three-dimensional (3D) seismic exploration technologies and new reservoir prediction methods to identify favorable gas-bearing zones in the ultra-deep volcanic formations.

The Bozhong Sag is the largest hydrocarbon-rich sag in Bohai, and CNOOC expects the discovery to expand exploration opportunities in the region.

The company did not disclose estimates of recoverable resources or plans for commercial development of the discovery.

“In recent years, CNOOC has continued to strengthen theoretical innovation in deep and ultra-deep oil and gas enrichment in basins with high heat flow and strong activity, and to intensify research on key technologies.

“Exploration in China’s offshore areas has achieved a major leap from shallow to deep and ultra-deep formations. The success of this well has opened up a new play for offshore ultra-deep natural gas exploration and expanded the scope of deep oil and gas exploration in Bohai.

“It is of positive significance for accelerating the ultra-deep exploration process in Bohai and for building a major gas province of one trillion cubic meters in Bohai,” said Xu Changgui, Chief Scientist and Chief Geologist of CNOOC.